The present invention relates to a vibration detector, in particular, relates to a vibration detector which detects the condition that two out of three components of a composite vibration have reached a predetermined value.
The present vibration detector can be utilized as a seismograph for measuring an earthquake. Usually, the vibration of an earthquake has three independent components, however, the analysis of two components in an horizontal plane is enough for determining earthquake damage.
There have been known some vibration detectors, some of which are as follows.